The present invention relates to systems that determine characteristics of a rotatable shaft, such as torque, axial location and axial alignment.
In equipment having rotatable shafts coupled together, torque, axial location and axial alignment are measured for use in monitoring the equipment for proper operation and life preservation. Monitoring of the rotatable shafts and couplings is performed to maintain a collinear relationship between the centerlines of coupled shafts and to maintain the torque transmitted through the shafts within predefined limits. Where angular variations between rotating shaft centerlines occurs, the degree of this variation is to be determined if realignment of the centerlines is to he performed. If flexible couplings are used to accommodate shaft realignment, the degree of misalignment is monitored to ensure that couplings remain within predefined operating limits for coupling life preservation. As rotatable shafts are often positioned within a confined area having a harsh environment, measurement of the characteristics of torque, axial location and axial alignment from the same apparatus that is capable of withstanding such environmental stress reduces the size and possible negative performance effects of the measuring apparatus.
In accordance with one aspect of the present invention there is provided an apparatus for obtaining an indication of torque, axial alignment and axial location for a shaft rotating about an axis of rotation, said apparatus comprising: a first set of detectable elements operably connected to the shaft and positioned parallel to the axis of rotation; a second set of detectable elements parallel to the axis of rotation and interlaced in a sensing plane with said first set of detectable elements, said second set of detectable elements having a variable relative position with respect to said first set of detectable elements; a third set of detectable elements positioned laterally to said first set of detectable elements and said second set of detectable elements in an alignment plane parallel to the sensing plane, said third set of detectable elements being positioned at an offset angle to the axis of rotation; and a plurality of sensors positioned to detect passage of said first set of detectable elements, said second set of detectable elements and said third set of detectable elements, each of said plurality of sensors producing a signal in response to detection of detectable elements; wherein relationships for signals produced from detection of said first, second and third sets of detectable elements with respect to a reference signal produced by detection of detectable elements in a plane separate from the alignment plane provides an indication of torque, axial alignment and axial location.